Artificial intraccular lenses (IOLs), used to replace damaged or diseased natural lenses in the eye, have been widely used in the last two decades. Typically, such intraocular lenses comprise an optical element and one or more haptics coupled thereto for properly positioning and centering the intraocular lens within the eye. These lenses have typically included hard polymeric or glass optical elements with metallic or polymeric supports.
During the past decade, the medical profession has made widespread use of intraocular lenses comprising polymethyl methacrylate (PMMA), a hard plastic composition. In general, PMMA lenses are cut on a precision lathe, using diamond cutters or injection molded, and then carefully post polished by a critical tumbling process in which the edges of the lenses are radiused and polished. Recently, workers in the art have utilized IOLs comprising a soft, biocompatible material, such as silicone. Silicone lenses have the advantage of being lighter in situ than PMMA lenses, and because they are flexible, they can be folded or rolled to reduce their size during implantation into the eye in accordance with conventional surgical procedures.
Methods of producing optical or ophthalmic components, such as IOLs, have not changed in principle in many years. The main requirements are that the optical surface be polished to a highly accurate shape. Currently, most IOLs are manufactured using the time-consuming, expensive, and quality-varying process of lathing. The hand or automated lathing processes for IOLs, as well as the steps currently necessary prior to the lathing process, which include sheet or rod forming, machining, button coring, tumble polishing, extraction, etc., are quite inefficient and require additional machinery for manufacturing the lenses.
Previously known techniques for casting molded concave-convex lenses, such as contact lenses, generally are not well suited for casting convex-convex IOLs. Known casting methods typically employ a male mold half and a female mold half, which interengage to form the mold space. The female mold half is horizontally disposed and upwardly facing. Lens material is deposited in the open female mold half, and the male mold half is pressed into engagement with the female mold half. The lens material is cured, the mold halves are separated, and the lens is removed from the mold. Casting a convex-convex lens requires filling a mold space formed between opposed female mold halves with lens-forming material, which has proven difficult or impossible using previously known techniques. Lens material deposited into the lower mold half typically is insufficient to fill the upper mold half, resulting in a void in the upper portion of the mold space and producing an inferior or defective lens.
Accordingly, there is a need in the art for improved molds and methods for casting ophthalmic lenses, and for lenses formed by such molds and methods.